I tested this so-called simulator and riddle me this... Why if I "pay down CCs balances $500/mo" for just 1 month, i get a 30pts bump up in score but if I chose "pay down CCs" with the same $500, I only get a 5 pts bump. Go figure?
In my experience it is more accurate than a roullette wheel, but slightly less than tarot cards, or crystal balls. IMHO.
The most significant limitation in offering a score simulator is that they cannot make it so accurate that the consumer can imput very specific changes as get an accurate score change. The scoring algorithm must be preserved as a trade secret by preventing reverse-engineerting.
Enabling one to input very specific changes and getting accurate results would, with only a bit of time, permit reverse engineering of the algorithm,and thus loss of their trade secret.
Fair Isaac produces the simulation, so it is not "inaccurate" so much as it is intentionally broad or vague, intentionally taking into account multiple factors.
I would not expect a score simulator to enable specifid inputs --> accurate outputs.